There is a need for small spherical particles high in lithium content. Such particles have applicability in nuclear reactors for breeding fusionable tritium (.sup.3 H) through capture by the lithium of free neutrons and may be employed in the core of a fission reactor or in a blanket region of a fusion reactor. For use in fission reactor cores where it is necessary to coat tritium breeding particles with a tritium impermeable shell lest the radioactivity of the circulating coolant rise to an intolerable level during reactor operation, spheroids represent the best configuration for uniform shell formation, e.g., with pyrocarbon and silicon carbide layers for containment of the bred tritium.
Spheroids of numerous metal oxides and mixed metal oxides have been produced by sol-gel or gel-supported precipitation methods. In a sol-gel method, the starting material is a colloidal dispersion (sol) of a compound in a liquid medium from which the compound can be turned into a gel form by dehydration or by changing the pH of the medium. In a gel-supported precipitation method, a starting material consists of a solution containing metal ions of the compound in a gelling medium from which the compound is precipitated in gel form by changing the pH value of the medium.
Spheroids produced by such methods have found use as catalyst supports, e.g., spheroids of alumina or mixed alumina-silicon oxides. Spheroids of uranium and thorium oxides are useful in nuclear reactors as nuclear fuel and for breeding fissionable material respectively.
A particularly promising lithium-containing material for use in tritium breeding is lithium aluminate (LiAlO.sub.2) which has a melting point greater than 1625.degree. C. Heretofore, attempts to form spheroids of lithium aluminate by sol-gel or gel-supported precipitation methods have been unsuccessful. The sol-gel method is unsuitable for producing lithium aluminate spheroids due to the failure to produce a lithium aluminate sol. An attempt to prepare lithium aluminate spheroids by gel-supported precipitation using a feed solution of aluminum nitrate, lithium nitrate and polyvinyl alcohol has resulted in leaching of the lithium ions when the spheroids are washed with 3 weight percent aqueous NH.sub.4 OH solution to rid the spheroids of NH.sub.4 NO.sub.3.